1. Field of the Invention
The present invention relates to a power transmission utilizing a belt and pulleys for a two-wheeled motorcycle.
2. Description of Relevant Art
There has been proposed a motorcycle power transmission including a V-belt and variable-diameter pulleys. With the proposed arrangement, one of the pulleys is mounted on the output shaft of the engine and the other pulley is mounted on the shaft for the driven wheel, the pulleys being interconnected by the V-belt. As the number of revolutions of the engine increases, a movable surface of the pulley associated with the engine is shifted so that the diameter of the pulley is increased, and a movable surface of the pulley associated with the driven wheel is shifted due to displacement of the V-belt so that the pulley diameter is reduced, whereby automatic speed changing is effected.
During operation of the prior power transmission, the movable members of the drive and driven pulley mechanisms are shifted in opposite directions as the engine speed varies, with the result that the V-belt is laterally displaced in opposite directions at the drive and driven pulleys. Accordingly, the V-belt tends to be twisted or distorted, putting undue stresses on the surfaces of the drive and driven pulleys with which the V-belt engages. Localized wear results in such belt-engaging surfaces, the service life and durability of the power transmission becomes poor, and the efficiency in power transmission is reduced. While a relatively long V-belt can take up a twist satisfactorily, short V-belts are unable to do so. Therefore, the conventional power transmission must necessarily be large in size, and cannot be applied to a small-sized two-wheeled motorcycle.
Another disadvantage with the known power transmission is that a clutch is located adjacent to the engine, such that the pulleys and belt between the engine and the rear wheel will necessarily be rotated with the rear wheel, including when the motorcycle is moved around with the engine turned off. It is therefore hard and laborious to manually move the motorcycle around while the engine is not in operation.